The present invention relates to a circuit breaker, such as circuit breaker for wiring, earth leakage breaker, etc., and specifically relates to an arc quenching device for an electromagnetic repulsion type circuit breaker.
The so-called de-ion type arc quenching device shown in FIG. 19 has been well known as this sort of an arc quenching device for a circuit breaker. This arc quenching device has a structure such that grids 2 with V-shaped cutouts for passing a moving contact member 1 are piled up with an adequate space away from each other, and supported with supporting panels 3 made of an insulation material (fiber, polyester glass mat laminate, etc.), and the grids 2 are fixed to the supporting panels 3 by adhering or press-fixing.
FIG. 20 is a longitudinal section view for showing a half of a power supply side of a circuit breaker with a de-ion type arc quenching device. An end or part 5a of a stationary contact member 5 formed unitarily with a power supply terminal 4 is bent back into a U-shape along a moving contact member 1, and a stationary contact 7 for contacting a moving contact 6 of the moving contact member 1 is attached to the end 5a of the stationary contact member 5. And, an arc horn 9 which leads an arc caused between the stationary contact 7 and the moving contact 6 toward the arc quenching device is attached to the stationary contact member 5.
Here, a current flowing through the bent back part 5a of the stationary contact member 5 and a current flowing through the moving contact member 1 positioned parallel to the bent back part 5a flow in opposite directions as indicated by arrows A in the figure, so that an electromagnetic repulsion force acts between these currents. Therefore, the moving contact member 1 is sprung up by this electromagnetic repulsion force when a large current, such as a short-circuit current and etc., flows. As a result, the moving contact member 1 is driven quickly to an open position shown by a chain line in the figure without awaiting the operation of a switching mechanism 11 actuated by the current limiting mechanism 10. At this time, an arc 8 receives a force toward an arrow B by a magnetic field of the current flowing through the bent back part 5a, and is urged deeply into the arc quenching device. This arc 8 is attracted further deeply into the arc quenching device by a bias of a magnetic flux of the arc itself owing to the existence of the grids 2, and the arc voltage rises by being cut by the grids 2. At the same time, the arc 8 is cooled with an arc quenching gas caused from the insulation material constituting the supporting panels 3, and is quenched in a short time together the pressure-rise in a molded case 12.
In regard to a circuit breaker of the electromagnetic repulsion type as shown in FIG. 20, it is disclosed in Japanese Laid Open Patent Publication No. 2-132716 that a circuit breaker has a magnetic driving core of a U-shape attached to the bent back part 5a of the stationary contact member 5 for concentrating a magnetic flux generated by the current flowing through the bent back part 5a so as to enhance action of the magnetic field to the arc.
In the circuit breaker of the prior art, in which the magnetic driving core is attached to the bent back part of the stationary contact member having the stationary contact and the de-ion type arc quenching device having the piled up grids in multi-stages is disposed so as to surround the moving and stationary contacts, since the grids are connected to supporting panels by press-fitting or adhesion, it takes many steps for fixing the grids to the supporting panels. Also, the supporting panels for supporting the grids and an insulation member for covering the magnetic driving core are separately disposed to thereby form a complicated structure in the prior art as disclosed in aforementioned Japanese Laid Open Patent Publication No. 2-132716. Furthermore, since the breaker has no effective means for shielding the grids from the arc, the grids contact the arc to melt and spread, so that the metal particles thereof may be attached to the switching mechanism resulting in impeding its smooth operation or reducing insulation strength between phases and poles.
In viewing the forgoings, an object of the present invention is to provide a circuit breaker which is simplified in the peripheral structure of an arc quenching device, prevented from damage in the grids by an arc, and improved in its breaking performance.